Nonlinear Spectral-Spatial Control and Localization of Supercontinuum Radiation

We present the first observation of spatiospectral control and localization of supercontinuum light through the nonlinear interaction of spectral components in extended periodic structures. We use an array of optical waveguides in a ${\mathrm{LiNbO}}_3$ crystal and employ the interplay between diffraction and nonlinearity to dynamically control the output spectrum of the supercontinuum radiation. This effect presents an efficient scheme for optically tunable spectral filtering of supercontinua.

Figure 1

(a) Spectrum of the generated supercontinuum radiation. (b) Schematic of the experiment illustrating the dispersion of the colors inside the array of optical waveguides.

Figure 2

(a) Spectrally resolved diffraction of the supercontinuum radiation (low input power of $17\mu \mathrm{W}$). Bottom: output color intensity profile. (b) Measured wavelength dispersion of the waveguide coupling (circles), corresponding fit to the experimental data (solid line), and estimated dispersion of the refractive-index modulation (indicated by arrows). (c) Numerically calculated propagation of the supercontinuum inside the sample. In simulations, the input spatial profiles of all spectral components have Gaussian shape with full width at half-maximum of peak intensity (FWHM) of $7.5\mu \mathrm{m}$.

Figure 3

(a) Spectrally resolved localization of the supercontinuum inside the central waveguide at input power of $P_{\mathrm{in}}=7.5\mathrm{mW}$. Bottom: output intensity distribution. (b) Measured (points) and calculated (lines) relative spectral power in the central waveguide as a function of the input power for five different spectral components, as indicated by labels. (c) Numerically calculated nonlinear propagation at $P_{\mathrm{in}}\simeq 7.5\mathrm{mW}$. In simulations, dimensionless power $P_0=M^{-1}\sum _{j=1}^M\int |A_j{|}^{2}dx$ is normalized to 1 mW and $\gamma \simeq -1.28\times {10}^{-4}$.

Figure 4

Reflection and tunneling of spectral components from an optically-induced defect. The array is probed (a) next to the defect; (b) one waveguide away; (c) two waveguides away.